Determining the exact location of a receiver in an environment can be quite challenging, especially when the receiver is located in an urban environment, or is located within a building. Imprecise estimates of the receiver's position may delay emergency personnel response times, or can negatively impact efforts to provide navigation to a desired destination. Positioning systems that transmit positioning signals used to estimate the position of a receiver are well known. Unfortunately, poor signal conditions found in urban and indoor environments often lead to estimates of receiver positions that indicate the receivers are indoors when the receivers are outdoors, or that indicate the receivers are outdoors when the receivers are indoors. Thus, solutions are needed to improve estimates of receiver positions, especially in urban areas or indoor environments.